Montreal — The Oasis Facebook page offers about what you’d expect from a juice manufacturer promoting its products. There are colourful photos of juice containers, a promotion offering free juice with the purchase of some cereal and a survey asking people to pick their favourite classic flavour: “pineapple, banana or orange?”

But since Saturday morning, the page has been under assault by consumers hurling virtual rotten tomatoes. “There is no limit to the baseness of companies,” read one typical message posted Monday afternoon. “Shame on Oasis,” another said.

The anger was sparked by a newspaper report that the producer of Oasis brand juices, Lassonde Industries Inc. of Rougemont, Que., had won an important court victory in a lengthy trademark battle against a small local soap producer called Olivia’s Oasis.

Quebec Superior Court had found Lassonde’s trademark claim groundless in 2010 and ordered the company to pay Olivia’s Oasis founder Deborah Kudzman $100,000 to cover her legal costs and an additional $25,000 in punitive damages.

But Lassonde appealed the award of damages, and La Presse reported Saturday that Quebec Court of Appeal had ruled in its favour, leaving Ms. Kudzman to pay her substantial legal bills.

The report unleashed a social media storm across Twitter and Facebook.

Quebecers were indignant that a successful juice business would go after a fledgling soap company on the dubious grounds that consumers might confuse their products.

Within hours, Lassonde was living a public-relations nightmare. Popular TV host Guy A. Lepage tweeted to his more than 100,000 followers that he would no longer be drinking Oasis, in protest of Lassonde’s treatment of Ms. Kudzman. In a sign of how powerful social media have become, Lassonde dispatched a senior executive to meet Ms. Kudzman on Easter Sunday with a promise to cover all her legal costs.

That executive, chief operating officer Jean Gattuso, said in an interview Monday that this was the first time the company had experienced such a backlash on Twitter and Facebook.

“We are entrepreneurs. We are people who react quickly to situations,” he said. “We are in business to sell products, and we didn’t like our consumers to be angry with us. We didn’t like the situation at all, and we reacted.”

On the other side of the dispute, Ms. Kudzman was equally surprised by the rapid reversal. “I could never in my wildest dreams have imagined the viral aspect of it. I think it’s almost unprecedented in Quebec,” she said. “I spent seven years fighting this, and within basically 48 hours, because of the outpouring of support, it was resolved.”

‘I spent seven years fighting this, and within basically 48 hours, because of the outpouring of support, it was resolved’

Ms. Kudzman left a career in advertising to start Olivia’s Oasis in 2004. She chose “Olivia” because it was her daughter’s name and her products contained olive oil, she explained. As for the “Oasis,” she said, “I wanted something that had a connotation of turning your bathroom into a place of serenity and peace.”

The serenity was short-lived. In 2005 she received a registered letter from Lassonde demanding that she immediately stop using the name, recall all her merchandise from stores and pay Lassonde any profits she had made. “To me it was utter nonsense,” she said.

A lawyer advised her she had a strong case, and in 2010 Superior Court Justice Dionysia Zerbisias agreed. The judge found “gaping visual dissimilarities” between the Oasis juice and Olivia’s Oasis brands, noting also that one was edible and the other not. She awarded the damages on the grounds that Lassonde had engaged in “menacing and abusive conduct.”

A three-judge appeal panel concluded on March 30 that Lassonde’s lawsuit had not overstepped the bounds and overturned the financial award. But then the social media stepped in as a sort of people’s court, giving Oasis the thumbs down.

The damage to Lassonde’s reputation over the course of a weekend was greater than any confusion that might have been caused by a soap branded with the word Oasis. Mr. Gattuso suggested the company would be more cautious in the future. “There is a lesson learned, absolutely,” he said.

Jean-Jacques Stréliski, an associate professor at HEC Montréal business school, told Radio-Canada that Lassonde’s experience is a cautionary tale for executives everywhere. “Every company has to be very aware of social media and not just treat social media as a platform for advertising,” he said. “They are a true force, one that reacts quickly and strongly and that can restrict you.”

Ms. Kudzman remains in awe of their strength but is also hoping to cash in on the unexpected publicity. On Monday she was in touch with her retailers to suggest they might want to stock up on more Olivia’s Oasis soap.